The production of signage, graphics on textiles or printed circuit boards, generally is accomplished in one of several ways. The first and least economical for multiple signs is hand painting. This of course requires a skilled sign painter and for each sign the sign painter must start over even though the signs are identical. Hand painted signs are effective in that a skilled sign painter can add a great deal of artistic skill to the finished product. They are particularly appropriate for single applications and for very large signs.
At the other end of the scale are signs produced by offset printing or lithography. Lithography has been used since at least as early as the nineteenth century. It involves a negative image made of an oily based material on a master plate (originally a stone hence the prefix "litho"). The plate with the master image is wetted with water and then inked with a material that adheres only to the oily material. The plate is passed through a press with paper so that the image is transferred to the paper as a positive. This old lithograph process is essentially the basis for today's "offset" printing where a positive image is transferred to the master and then to the final paper hence the term offset. Careful preparation and elaborate offset presses permit overprinting of various colors (three or four for example) so that many thousand copies can be made from one master. Lithography or offset printing has, because of its flexibility and economies, withstood the rigors of time and has recently replaced set type or hot type printing to the extent linotype machines and the like have disappeared from use all in a matter of a few years.
In between the sign painter and lithography or offset printing is silk screening, a process that combines the features of both. It provides flexibility to the sign-painter/artist while allowing multiple copies. Silk screen, depending on the process used, can reproduce hundreds of copies without degradation of the master.
The process, in its historical sense, can be likened to making a stencil. The artist or sign painter first prepares the screen and then blocks out the areas that are not to be printed. In effect a "stencil" is prepared. However the "stencil" consists of a piece of woven and porous fabric, traditionally silk, where the fabric is made impervious to ink in all places except where the printing is wanted. Once the "silk screen" is prepared, it may be put in a printing frame so that paper or other material may be placed under the screen and ink applied to the opposite side of the screen then "squeegeed" onto the paper thereby making an image on the paper, wood, metal or textiles. By using multiple screens it is possible to work in colors so that multiple color images may be made. The traditional silk screen process which is still practiced in artist communities, involved a good deal of hand work in making the image in a negative fashion on the silk screen with a substance that is impervious to the ink that will be used. In recent years, photo transfer processes have been developed so that the "stencil" like image can be readily transferred to the screen using a photo process.
Silk screening, when used commercially is a relatively easy and inexpensive procedure that takes minimum amount of equipment yet will make multiple copes, up in the hundreds. However, the screens are not easily stored for future use and are often cumbersome.
The principal drawback in silk screening is the time element involved in preparing the screen. Even with the advent of the photo process, silk screen work requires a good deal of "artistic" ability with little or no capability to edit or the like. For these reasons silk screening has been generally limited to the artistic fields or to rather mundane signs with little imagination,
In the past ten years there has been almost an explosion in desk top publishing. Desk top publishing provides a capability not available several years ago except to the most sophisticated printing establishment, Words such as fonts, point size, kerning and the like all associated with printing, have now joined the everyday vocabulary. Not only has desk top publishing given the personal computer user the composition capability of large scale printing firms; it also provides the corollary capability of graphic composition that permits a mix of print and graphics, something only the most sophisticated printing firms had until recently. The graphics may consist of "canned" items such as borders or preconceived designs, but also may permit the user to literally "draw" his or her own design while intermingling text with the design.
Once the text and design are completed, current technology such as laser printing permits the material to be printed and thus previewed. Should the design be in more than one color, then separate designs can be obtained and previewed for each color. State of the art software publishing programs permit these graphic images and textual material to be "translated to bit maps" so that at a density of, for example 300 dots or bits per inch, the image is sent to a printer capable of registering the image to that resolution.
This invention combines the classical art of silk screening with desk top publishing.
It is the principal object of this invention to provide an apparatus driven by a computer that will make and print a silk screen pattern.
It is another object of this invention to provide an apparatus that will make a silk screen of synthetic non porous sheet material is less expensive or more economical than silk.
It is also an object of this invention to provide an apparatus where the "screen" is non porous except where the image is desired.
It is still another object of this invention to provide an apparatus wherein a pattern of holes can be transferred to a non porous screen by means of a laser.